Power Quality development using PV based boost cascaded inverter system is one of the reliable methods. This paper handle with modeling and fuzzy logic control of boost to boost cascaded three phase inverter system with PV as source. MATLAB simulink model for BBCIS has been developed using the elements of simulink and cascaded loop investigations are performed with PI and Fuzzy Logic Controllers. The dynamic responses of the above systems are compared in terms of time domain parameters. The consequences point to that maximum power is obtained with minimum THD using FLC.

1. International Journal of Power Electronics and Drive System (IJPEDS)
Vol. 8, No. 3, September 2017, pp. 1389~1400
ISSN: 2088-8694, DOI: 10.11591/ijpeds.v8i3.pp1389-1400  1389
Journal homepage: http://iaesjournal.com/online/index.php/IJPEDS
Modeling and Fuzzy Logic Control of PV Based Cascaded Boost
Converter Three Phase Five-level Inverter System
Guruswamy Revana, Venkata Reddy Kota
Department of Electrical and Electronics Engineering, Jawaharlal Nehru Technological University Kakinada, India
Article Info ABSTRACT
Article history:
Received Apr 8, 2017
Revised Jul 10, 2017
Accepted Aug 1, 2017
Power Quality development using PV based boost cascaded inverter system
is one of the reliable methods. This paper handle with modeling and fuzzy
logic control of boost to boost cascaded three phase inverter system with PV
as source. MATLAB simulink model for BBCIS has been developed using
the elements of simulink and cascaded loop investigations are performed
with PI and Fuzzy Logic Controllers. The dynamic responses of the above
systems are compared in terms of time domain parameters. The
consequences point to that maximum power is obtained with minimum THD
using FLC.
Keyword:
Boost converter
Multi-level Inverter
PI controller
Solar panel
Copyright ©2017 Institute of Advanced Engineering and Science.
All rights reserved.
Corresponding Author:
Guruswamy Revana,
Department of Electrical and Electronics Engineering,
Jawaharlal Nehru Technological University Kakinada,
Kakinada, Andhra Pradesh, India.
Email: guru_revana@yahoo.com
1. INTRODUCTION
Due to privileged efficiency and slighter size, photovoltaic (PV) inverters without isolation
transformers become more attractive in grid-connected PV systems [1]–[4]. Besides, generally they are not to
routinely decrease DC current injection [5], which causes the saturation of distribution transformers in the
grid and results in bad power quality, higher loss, Over heating in the power system [1], [6]. As a result,
standards and regulations have been formulated to limit PV inverter DC injection to the grid. To decrease DC
injection, some control methods have been proposed [1], [6], [7]. The methods of DC current booster
repression can be mainly classified into four categories: blocking DC current with the capacitor, novel
inverter configuration with DC current suppression capability, current-detection manages and voltage-
detection organizes. The process of overcrowding DC current with the capacitor uses a serially connected
capacitor between the inverter and the grid [12]. It requires a bulky and expensive capacitor and may cause
extra loss. Guo et al developed a method to block DC current by using a virtual capacitor; however, the
dynamic response of the closed-loop control system was affected by the virtual capacitor. The method of
applying inverter topology with DC current suppression ability uses inherent structure of the inverter
topology which can prevent DC current from injecting into the grid, e.g., the half-bridge inverter [13].
However, few practical topologies exist.
The way of current-detection control uses current sensors to find the DC current booster to the grid,
but its effectiveness is limited by the accuracy of sensor due to the inherent zero-drift characteristic of Hall-
effect current sensors. To solve the zero drift problems, an auto-calibrating inverter has been proposed by
Armstrong [14]. However, this method requires determining the switching state of the H-bridge in order to
measure the inherent zero-drift of the system. Sharma first detected a method of DC offset voltage. The grid
current was removed by feeding back the DC offset voltage to the PI controller. DC offset detected at the

2.  ISSN: 2088-8694
IJPEDS Vol. 8, No. 3, September 2017 : 1389–1400
1390
output of the low-pass filter is fed back to the controller. A mathematical model is presented in this paper.
However, the experimental results under grid mode were not given. The voltage-detection control method
uses sensors to detect the DC voltage offset across the ripple filter [15]. This method indicates that low DC
voltage across the filter can be measured, which is sensitive to noise. A DC offset detection method is
proposed by Buticchi [16]. However, this method needs a nonlinear inductor. Hence, a customized inductor
should be designed according to specific systems. He and Xu [17] used a voltage sensor at the output of the
inverter which consists of a differential amplifier and a low-pass filter. Alfock and Bowtell [19] continued
studying this method by establishing the mathematical model and verified it.
The above literature does not deal with BBCIS based PV system with MPPT. This work deals with
FLC based MPPT for BBCIS systems. This paper is organized as follows: Section II describes the details of
proposed system. Section III analyzes the results of BBCIS with and without MPPT. Section IV provides
experimental results to verify the theoretical analysis the conclusion is given in Section V.
2. PROPOSED SYSTEM
The block diagram of existing system is shown in Figure 1. The output of PV is stepped up using
boost converter. The output of three phase inverter is employed on to the load. The block diagram of
proposed system is shown in Figure 2. Two boost converters are cascaded to increase the voltage gain. The
FLC is proposed to improve the dynamic response.
Figure 1. Block diagram of existing system
Figure 2. Block diagram of proposed system
3. SIMULATION RESULTS
PV inverter system with cascaded boost converter is shown in Figure 3. Scopes are connected to
measure voltage, current and power. The output of PV system is boosted using two boost converters. The DC
output is converted into AC using three phase inverter. The change in voltage due to reduction in light
intensity is shown in Figure 4. The voltage reduces from 48 to 44 volts. The output voltage of boost converter
is shown in Figure 5. The output voltage reduces from 190 to 170 volts. The switching pulses for M2, M4 and
M5 are shown in Figure 7. PMW pluses are applied to the Switches. The phase current waveforms are shown
in Figure 8. The load current is smoothened by the load inductance. The output power reduces from 230W to
190W as shown in Figure 9. The frequency spectrum for current is shown in Figure 10 and the THD is
10.1%. Lowest frequency is 50Hz and highest frequency is 900Hz. Fundamental component of current is
3.5A. Fifth harmonic is predominant and other harmonics are negligible.
Load
PV System
Boost
Converter
3 Phase
Inverter Grid

3. IJPEDS ISSN: 2088-8694 
Modeling and Fuzzy Logic Control of PV Based Cascaded Boost Converter … (Guruswamy Revana)
1391
Figure 3. Circuit diagram for BBCIS without MPPT
Figure 4. Output voltage of Solar System
Figure 5. Output voltage of Boost to boost converter
Figure 6. Switching pulses for S1, S3 and S5 inverter
Vs
Volts
time, secs
time, secs
VB
Volts
time, secs
Vg2
Volts
Vg4
Volts
Vg5
Volts

4.  ISSN: 2088-8694
IJPEDS Vol. 8, No. 3, September 2017 : 1389–1400
1392
Figure 7. Output voltage waveforms
Figure 8. Output current waveforms
Figure 9. Output power
Van
Volts
Vbn
Volts
Vcn
Volts
time, secs
ia
Amp
ib
Amp
o
ic
Amp
time, secs
Po
Watts
time, secs

5. IJPEDS ISSN: 2088-8694 
Modeling and Fuzzy Logic Control of PV Based Cascaded Boost Converter … (Guruswamy Revana)
1393
Figure 10. Frequency spectrum for the current
Closed loop PI controlled system with MPPT is shown in Figure 11. Actual power is measured and
it is compared with reference power and the error is applied to PI controller. The output of PI controller is
used to generate the pulses for the switches of the boost converter. The output of PV system is shown in
Figure 12. The output of BC is shown in Figure 13. The output voltage is brought back to normal value. The
three phase output voltages are shown in Figure 14. The three phase currents are depicted in Figure 15. The
power output is shown in Figure 16 and it is maintained constant at 230W. The frequency spectrum for the
current is shown in Figure 17 and the THD is 8.1%. Fundamental component of current is 2.58A. Fifth &
seventh harmonics are predominant and other harmonics are negligible.
Figure 11. Circuit of BBCIS with MPPT and PI controller

6.  ISSN: 2088-8694
IJPEDS Vol. 8, No. 3, September 2017 : 1389–1400
1394
Figure 12. Output voltage of Solar System
Figure 13. Output voltage of boost to boost converter
Figure 14. Output voltage waveforms of Inverter
Vs
Volts
time, secs
time, secs
VB
Volts
Van
Volts
Vbn
Volts
Vcn
Volts
time, secs

7. IJPEDS ISSN: 2088-8694 
Modeling and Fuzzy Logic Control of PV Based Cascaded Boost Converter … (Guruswamy Revana)
1395
Figure 15. Load current waveforms
Figure 16. Output power
Figure 17. Frequency Spectrum for Load Current
The closed loop system with FLC is shown in Figure 18. The PI controller is substituted by FLC.
The step reduction in voltage is shown in Figure 19. The output voltage of boost to boost converter is shown
in Figure 20. The output voltage has settled at 200V. The three phase voltage and current waveforms of
BBCIS are shown in Figures 21 and 22 respectively. The output power is shown in Figure 23 and is equal to
230W. The frequency spectrum for the current is shown in Figure 24 and the THD is reduced to 5.67%. The
magnitude of fifth harmonic is 5.5% and the magnitude of seventh harmonic is 3%.
ia
Amp
ib
Amp
o
ic
Amp
time, secs
Po
Watts
time, secs

8.  ISSN: 2088-8694
IJPEDS Vol. 8, No. 3, September 2017 : 1389–1400
1396
Figure 18. Circuit of BBCIS with MPPT using FLC
Figure 19. Output voltage of solar system
Figure 20. Output voltage of boost to boost converter
Po
Watts
time, secs
Po
Watts
time, secs

9. IJPEDS ISSN: 2088-8694 
Modeling and Fuzzy Logic Control of PV Based Cascaded Boost Converter … (Guruswamy Revana)
1397
Figure 21. Voltage waveforms of Inverter
Figure 22. Load current waveforms
Figure 23. Output power
Van
Volts
Vbn
Volts
Vcn
Volts
time, secs
time, secs
ia
Amp
ib
Amp
o
ic
Amp
Po
Watts
time, secs

10.  ISSN: 2088-8694
IJPEDS Vol. 8, No. 3, September 2017 : 1389–1400
1398
Figure 24. Frequency Spectrum for Current
The summary of time domain parameters using PI and FLC is given in Table 1. It is observed that
the settling time and it’s deviation from the set value are very much reduced using FLC. The summary of
output power and THD is given in Table 2. The FLC incorporated closed gives required power and lower
THD in the load current. The settling time is reduced from 0.3 to 0.02 seconds and the steady state error is
reduced from 2.8V to 0.7V. The THD in FLC based BBCIS system is reduced to 5.67%.
Table 1. Time domain parameters
Controller Rise time (s) Peak time (s) Setting time (s) Steady state error (Volts)
PI 0.05 0.23 0.3 2.8
FLC 0.01 0 0.02 0.7
Table 2. Comparison of Power & THD
Control Po THD
Without MPPT 190w 10%
With MPPT PI 230w 8.14%
With MPPT & Fuzzy 230w 5.67%
4. EXPERIMENTAL RESULTS
The hardware is engineered and tested in the Department. The specifications for the hardware used
are given in Table 3.
Table 3. Hardware specifications
Component Specification
N-channel MOSFET IRF 840
Current rating 8A
Voltage 500V
Gate voltage 10V
Diode 1N4007
Controller PIC16F84A
Driver IR2110
Transformer 230/0-15V 50Hz
Regulator LM7812
Regulator LM7805
The hardware snapshot for the CFLI system is reported in Figure 25. The hardware consists of
control board, MLI board and driver board. The DC input voltage reported in Figure 26. Driving pulses for
S1 and S5 are reported in Figures 27 and 28 respectively. The output of MLI for line to neutral voltage is

11. IJPEDS ISSN: 2088-8694 
Modeling and Fuzzy Logic Control of PV Based Cascaded Boost Converter … (Guruswamy Revana)
1399
reported in Figure 29. The output of line to line voltage is reported in Figure 30. The output voltage has five
levels.
Figure 25. Hardware Snapshot Figure 26. Output Voltage of Boost Converter (60V)
Figure 27. Driver output pulse S1 Figure 28. Driver output pulse S5
Figure 29. Line to Neutral voltage Figure 30. Line Voltage
5. CONCLUSION
Closed loop BBCIS with PI and FLC were modeled and simulated successfully using simulink. The
hardware is developed and tested in the laboratory. The investigation indicated that fuzzy logic controlled
BBCI system gives rated power with 5.6% of THD. The output power is maintained at 190W using MPPT.
The proposed controller sustains constant output power with reduced harmonic content. The analysis and
simulation showed that constant real power can be maintained by using FLC. The advantages of proposed
system were high voltage gain, low THD and reduced hardware. The disadvantage is that the proposed
system requires two boost converters and FLC. The present work deals with comparison of responses of
BBCIS with PI and FL controllers. The comparison between PI and ANN will be done in the near future.

12.  ISSN: 2088-8694
IJPEDS Vol. 8, No. 3, September 2017 : 1389–1400
1400
REFERENCES
[1] R. Gonzalez, E. Gubia, J. Lopez, and L. Marroyo, “Transformerless singlephase multilevel-based photovoltaic
inverter”, IEEE Trans. Ind. Electron., vol. 55, no. 7, pp. 2694–2702, Jul. 2008.
[2] T. Kerekes, R. Teodorescu, P. Rodriguez, G. Vazquez, and E. Aldabas, “A new high-efficiency single-phase
transformerless PV inverter topology”, IEEE Trans. Ind. Electron., vol. 58, no. 1, pp. 184–191, Jan. 2011.
[3] H. Baeberlin, “Evolution of inverters for grid connected PV-Systems from 1989 to 2000”, in Proc. 17th Eur.
Photovoltaic Solar Energy Conf., Munich, Germany, Oct. 22–26, 2001, pp. 426–430.
[4] J. M. Carrasco, L. G. Franquelo, J. T. Bialasiewicz, E. Galvan, ´ R. C. Portillo Guisado, M. A. M Parts, J. I. Leon,
and N. Moreno-Alfonso, “Power-electronic systems for the grid integration of renewable energy sources: A
survey”, IEEE Trans. Ind. Electron., vol. 53, no. 4, pp. 1002– 1016, Jun. 2006.
[5] D. G. Infield, P. Onions, A. D. Simmons, and G. A. Smith, “Power quality from multiple grid-connected single-
phase inverters”, IEEE Trans. Power Del., vol. 19, no. 4, pp. 1983–1989, Oct. 2004.
[6] S. B. Kjaer, J. K. Pedersen, and F. Blaabjerg, “A review of single-phase grid-connected inverters for photovoltaic
modules”, IEEE Trans. Ind. Appl., vol. 41, no. 5, pp. 1292–1306, Sep. 2005.
[7] W. M. Blewitt, D. J. Atkinson, J. Kelly, and R. A. Lakin, “Approach to low-cost prevention of DC injection in
transformerless grid connected inverters”, IET Power Electron., vol. 3, no. 1, pp. 111–119, Jan. 2010.
[8] V. Salas, E. Ol´ıas, M. Alonso, F. Chenlo, and A. Barrado, “DC current injection into the network from PV grid
inverters”, in Proc. IEEE Photovoltaic Energy Convers. Conf., Waikoloa, HI, USA, May 2006, pp. 2371– 2374.
[9] AS 4777.2, Grid connection of energy system via inverters. Part 2: Inverter requirements Australia, 2002.
[10] “IEEE recommended practice for utility interface of photovoltaic (PV) systems”, IEEE Standard 929-2000, Apr. 3,
2000.
[11] ER G83/1, “Recommendations for the connection of small-scale embedded generators (up to 16 A per phase) in
parallel with public low-voltage distribution networks”, Eng. Recommendation, U.K., Sep. 2003.
[12] R. Gonzalez, J. L ´ opez, P. Sanchis, and L. Marroyo, “Transformerless ´ inverter for single-phase photovoltaic
systems”, IEEE Trans. Power Electron., vol. 22, no. 2, pp. 693–697, Mar. 2007.
[13] N. Mohan, T. Undeland, and W. Robbins, Power Electronics: Converters, Applications and Design. New York,
NY, USA: Wiley, 2002.
[14] M. Armstrong, D. J. Atkinson, C. M. Johnson, and T. D. Abeyasekera, “Auto-calibrating DC link current sensing
technique for transformerless, grid connected, H-Bridge inverter systems”, IEEE Trans. Power Electron., vol. 21,
no. 5, pp. 1385–1393, Sep. 2006.
[15] L. Bowtell and A. Ahfock, “Direct current offset controller for transformerless single-phase photovoltaic grid-
connected inverters”, IET Renew. Power Gener., vol. 4, no. 5, pp. 428–437, Sep. 2010.
[16] G. Buticchi, E. Lorenzani, and G. Franceschini, “A DC offset current compensation strategy in transformerless
grid-connected power converters”, IEEE Trans. Power Del., vol. 26, no. 4, pp. 2743–2751, Oct. 2011.
[17] G. He and D. Xu, “A novel DC loop current control strategy for paralleled UPS inverter system based on decoupled
control scheme”, in Proc. Int. Symp. Ind. Electron., Hangzhou, China, May 28–31, 2012, pp. 70–75.
[18] K. Masoud and G. Ledwich, “Grid connection without mains transformers”, J. Electr. Electron. Eng., vol. 19, no.
1/2, pp. 31–36, 1999.
[19] T. Ahfock and L. Bowtell, “DC offset elimination in a single-phase gridconnected photovoltaic system”,
Australasian Universities Power Engineering Conference, Melbourne, Australia, Dec. 10–13, 2006.